I am getting a message the the server on my computer is unavailable.

I am getting a message the the server on my computer is unavailable. I can use my sons computer that is 15 Miles away from me . This is displayed when I drop down the list of serves I am connected to. When I start the plex I am on my sons Plex server and not mine and I can not switch to mine because it is unavailable ???

It was fine yesterday and I guess something changed that I am not aware of .
I have uninstalled and reinstalled
Can you help me get reconnected to the server on the home computer

Thanks
Plano Pat